Astronomy 2021A/B Chapter Notes - Chapter 0: Ethane, Methanol, Sun Chemical
4 Oct 2017
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Chapter 9: searching for life in our solar system. No world besides earth has an atmosphere that we could breathe or abundant surface water that we could drink. Few worlds have atmospheres that offer any protection from dangerous ultraviolet radiation from the sun. Habitability generally means an environment in which life of some kind might survive. Most obvious requirement for life is a set of chemical elements with which to make the components of cells. Life on earth uses about 25 of 92 naturally occurring chemical elements. Oxygen, carbon, hydrogen, nitrogen make up about 96% of the mass of living organisms. The presence of most or all of the elements used by life on earth is a reasonable first requirement for life in general. Can be met by almost any world. As long as condensation and accretion can occur, we expect the resulting worlds to contain the elements needed for life. Good reason to think life elsewhere is carbon-based.
